The following account of the prior art relates to one of the areas of application of the present application, hearing aids.
Hearing assistance devices (acoustic or bone-anchored hearing aid, implant, headset, telephone etc.) manipulate their input signals in deliberate ways before presenting them to the ear. In some applications this manipulation includes aspects (e.g. gain, frequency response, compression, noise reduction) intended to compensate for a deviation from normal function in the cochlea of the user. At present, the user's cochlear function is grossly estimated on the basis of either assumed average function (in the case of applications for supposedly normal-hearing listeners) or diagnostic indicators (in the case of hearing-impaired listeners). In both cases, it is assumed that the user's cochlear function is stable over time. Furthermore, any diagnostic indicators (e.g. hearing thresholds) are at best only indirectly correlated with the physiological status of the cochlea. Thus the signal manipulation taking place in the hearing device cannot truly take account of the current functional status of the cochlea which is receiving and transducing those signals for the user to hear. This limits the user benefits which can be obtained.
[Mercier et al, 2012] deal with the topic of energy extraction from electrochemical processes in the inner ear. It is proposed to use the Endocochlear potential (EP) generated in the inner ear as a power source for electronic devices, e.g. to power chemical and molecular sensors, or drug-delivery actuators for diagnosis and therapy of hearing loss and other disorders.
US2012300964A1 describes a method of testing a hearing ability of a user. A hearing aid is adapted to output a sound to test a hearing ability of a user, to detect an electrical signal generated in a body of the user as a result of the output sound, to amplify the electrical signal detected by an electrode unit, and to determine an amplification ratio of a surrounding sound detected by the hearing aid based on characteristics of peaks of waveforms of the amplified signal.
EP2200347A2 deals with a method of operating a hearing instrument based on an estimation of present cognitive load of a user, e.g. by measuring an ambulatory electroencephalogram (EEG), e.g. using suitable electrodes in the surface of a hearing aid shell where it contacts the skin inside or outside the ear canal.